Is it possible to render a movie on a single computer in blender?
It is possible to render a movie on a single computer. It depends on what movie it is. If you choose a style that renders extremely fast, it is possible. Nothing like the ones Disney make though. Not even remotely close.  

Let's say you are rendering a movie that is 1 hour and 30 minutes. Let's say 1 frame of that movie renders extremely fast - 2 minutes. You are rendering 90 minutes of video, that is 5400 seconds and you probably need 30 frames for each second so that's 162000 frames. Each takes 2 minutes, so that comes to 324000 minutes that is 5400 hours and that is 225 days. So if you run your computer for 225 days, you will render your movie. 

Now try having a simple scene that is inside some room and needs light that comes from a window(so it needs light that bounces around) and render it in 4k resolution in 2 minutes... That is a very hard thing to do. Chances are you will need a few hours at least for a single frame of any of the Disney movies on a single PC. That's why it is impossible to render on a single PC.